Hunters seldom agree as to the length of time a big game carcass should be aged. What is involved in the aging process? When is
it beneficial to age game meat? Under what
conditions is it inadvisable to age game? This
pamphlet is concerned with answers to these
questions.

Let's assume that the hunter has made his kill and
properly dressed the carcass. Now we want to know
what he should do from the time the carcass is
eviscerated until it is ready to be cut into steaks and
roasts.

What is Aging?

Aging of meat--also called seasoning, ripening or
conditioning--is defined as the practice of holding
carcasses or cuts at temperatures of from 34ºF to
37ºF. Thus enzymes (cateptic or proteolytic) function
to break down some of the complex proteins
contained in the muscle.

Quick aging of beef is brought about
commercially by holding beef at temperatures of 62ºF
to 65ºF for 2 or 3 days. High relative humidity is
maintained to prevent dehydration; ultraviolet lamps
are used to prevent microbial growth.

Some Meat Should not be Aged

Aging usually results in improvement of
tenderness and flavor. However, not all meat should
be aged. Aging carcasses with little or no fat cover is
not recommended by meat specialists. These
carcasses lose moisture rapidly; excessive weight loss
and surface discoloration of lean meat result. In
addition, lean meat is exposed and is susceptible to
deterioration through microbial growth. Slime
formed by bacteria and mold growth then must be
trimmed.

Because grinding or chopping tenderizes meat,
aging is not justified for carcasses that are to be
ground, or made into, bologna, frankfurters or other
sausages.

Pork never is aged because the animals are young
when slaughtered and the meat is naturally tender.
Additionally, the unsaturated fats found in pork fat
oxidize during aging causing rancidity and off flavor.

Veal has very little protective fat covering and is
high in moisture; thus it does not lend itself to aging.
Most markets require the "hog style" veal carcass
(skin on) because it prevents the outer surface of the
carcass from becoming dark and dry.

The above examples show that not all meat
benefits from aging. Whether or not game carcasses
should be aged can be determined by first
understanding the changes which occur during aging.

Changes in Tenderness

Immediately after the animal's death all meat
decreases in tenderness ( Figure 1). This is because
muscle fibers shorten and harden as a result of rigor
mortis. The changes are similar to those which occur
during muscle contraction. The third day after
slaughter, meat which has been cooled at 34ºF has
returned to its original tenderness level.

For example in Figure 1: Immediately after death
all meat decreases in tenderness. From one to
approximately 14 days, tenderness increases at a
constant rate. After 14 days aging, tenderness
continues to increase,but at a much slower rate.

If the carcass is to be made into chops, steaks and
roasts, additional aging at 34ºF is often
recommended. At 34ºF and high relative humidity,
it usually takes 10 to 14 days for bacterial slime to
develop on meat. This, along with the fact that
tenderization proceeds more slowly after 14 days
aging than it does from 3 to 14 days, is the reason
aging should be limited to a maximum of 2 weeks.

Aging game that has been skinned often results in
drying and high weight loss. For this reason properly
chilled game should be aged with the hide on unless
it is to be stored in a cooler where the humidity is
high. Some people think that leaving the hide on
causes off flavor, especially in antelope. However,
research on factors affecting flavor of game has failed
to substantiate this claim.

Many meat processors do not recommend aging
game. One reason for this is that much of the game
delivered to a meat processor has already been aged
long enough. Quick aging of the meat often occurs
because the game carcass could not be chilled at 34ºF
after the kill.

Aging Game Shot in Warm Weather

A 65ºF temperature at the time of the kill will
result in less toughening and hardening of the muscles
due to rigor mortis than will a temperature of 34ºF.
In addition, the action of natural enzymes which are
responsible for tenderness increases is much faster at
65ºF. Thus, aging at 65ºF for 3 days gives the same
amount of tenderization as the more conventional
aging temperature of 34ºF for 2 weeks. Therefore,
game which is killed when the temperature is near
65ºF and held at this temperature should not be
aged.

Game slaughtered in the cold months of
November and December should be aged longer than
game slaughtered in the warm months of September
and October. Alternating temperatures, such 65ºF
days and 30°F nights speeds up the aging
process. Under these conditions aging game 1 week
or less is recommended.

During warm hunting seasons, special care should
be taken to keep the carcass cool. It should be kept
in the shade and allowed as much air circulation as
possible. Transport the carcass to camp and skin it if
the temperature is expected to be above freezing the
first night after the kill. Cheese cloth or light cotton
bags should be used to protect the meat from insects
and dirt. Because they hold in heat and cause meat
to spoil rapidly, airtight game bags or tarps should not
be used.

Aging Game Shot in Cold Weather

Game carcasses under 100 pounds often chill
rapidly if the temperature is below freezing at the
time of slaughter.

Muscle contraction or rigor mortis hardens the
muscle to a greater extent than if the temperature is
above freezing. Very rapid chilling and hardening
causes meat to be tough. This condition is known as
cold shortening; it will occur if the internal muscle
temperature drops to 32ºF within 12 hours after the
kill. Leaving the hide on will help prevent cold
shortening and also help to keep the carcass from
freezing.

Carcasses which undergo cold shortening should
be aged at 34ºF. If the carcass is frozen while
hanging, little additional tenderization will occur
because enzyme action is very slow at freezing
temperatures. Frozen carcasses should be thawed and
maintained at 34ºF. Alternate periods of freezing
and thawing should be avoided because these
temperature variations lower meat quality.

Recommended Aging Times

Antelope carcasses shold be cut and wrapped for
the freezer within 3 days after the kill. This short
aging period helps prevent the "liver-like" or "mushy"
texture often found in antelope meat.

Deer, sheep, goat, cow elk and cow moose
carcasses should be cut approximately 7 days after the
kill. If they have been held at higher temperatures
(above 40ºF) the meat should be cut before 7 days of
aging are completed.

Under ideal conditions bull elk and moose
carcasses should be cut after a 14-day aging period at
34º to 37ºF. However, these carcasses are seldom
handled under ideal conditions. Slow chilled
carcasses and carcasses that have been in camp for a
few days require less aging.

The preceeding recommended aging periods are
sufficient for tenderness and flavor development in
most game carcasses. These aging periods are not
needed if game carcasses are to be ground, cured or
made into sausage. In addition, most meat recipes
utilize moist heat cooking methods which tenderize
the meat and shorten the needed aging period.

Do not age any game carcass if it was shot during
warm weather and not chilled rapidly, if the animal
was severly stressed prior to the kill, if gunshot areas
are extensive, or if the animal was under 1-year of
age. Aging has already occurred if the carcass has
been in camp for 1-week in relatively warm weather.
No further aging is recommended.

Aging periods longer than those recommended
are often accompanied by extensive bacaterial growth
on the game carcasses and by drying and discoloration
of the meat. Reducing the aging period reduces
bacterial growth on the carcass. At present there
does not appear to be any evidence that there is a
helath risk in eating properly cooked game meat.
Nevertheless, adequate precautions with regard to
aging time and aging temperature should be followed.

Aging Carcass Parts

Individuals who cut and wrap their own game may
want to process the entire carcass--except the loin and
rib cuts--three days after the kill. This practice
eliminates drying and spoilage on carcass parts other
than the loin and rib that are often ground or moist-
heat cooked.

The loin and rib cuts, which usually have some fat
cover to protect against drying and are dry-heat
cooked, could then be aged in a cool, clean place up
to 2 weeks or until deterioration due to drying or
microbial growth, indicated that aging should be
discontinued. No justification exists for the idea that
fat should be trimmed from game before meat is
aged. The fat protects the meat during aging.
However, trimming fat after aging is recommended to
avoid undersirable flavors which are often associated
with the fat.

Consideration for the Processor

Cooler space is a factor which often limits aging
of meat in commercial operations. Proper aging of
meat and proper meat handling in general could be
facilitated for commercial processors if the game kill
were distributed over a wide period by staggering the
opening dates of the hunting season more than they
are staggered at the present time.

Summary

Many practical considerations must ultimately
determine whether to age or not to age game meat.
Among these are the temperature at the time of kill,
the chilling rate, the internal temperature of the
muscle after chilling, the youthfulness of the animal,
the relative humidity, the amount of weight loss the
hunter is willing to sacrifice, the processing procedure
and the cooler space and labor available if the game
is to be processed commercially.

Under ideal conditions, age antelope 3 days, deer,
sheep, goat, cow elk and cow moose 7 days and bull
elk and bull moose 14 days after the kill at 34ºF. If
the temperature is higher, the aging period should be
shorter. Game which is killed when the temperature
is 65ºF or above and held at this temperature over 1
day should be cut immediately. Game that is to be
ground or chopped does not need to be aged.